As high-quality and high-speed wireless communications in indoor environments has become important, femto base stations are being widely used as small-sized base stations installed in indoor areas of commercial facilities, office buildings or the like. In particular, as long Term Evolution (LTE) has been recently introduced as a new air interface replacing Wideband-Code Division Multiple Access (W-CDMA), LTE femto base stations are anticipated to be widely used. Meanwhile, as high-performance multi-functional mobile stations such as smart phones have become prevalent, various services using location information of the mobile stations are being provided. However, in indoor environments. Global Positioning System (GPS) is out of service and the sensitivity of a geomagnetic sensor is low. For this reason, in order to provide such a service using location information of a mobile station to a user in an indoor area, it is effective that a mobile station measures a location thereof (i.e., performs a positioning) by using a radio signal from a femto base station. Typical indoor positioning techniques include RF (Radio Frequency) pattern matching, which may be referred as RF fingerprint, and multi-point positioning such as three-point positioning, for example.
Related art is disclosed in Japanese Laid-open Patent Publication No. 10-84571, Japanese Laid-open Patent Publication No. 2001-428222, and Japanese Laid-open Patent Publication No. 2005-147747.
However, since ail the aforementioned positioning techniques mainly use wireless quality information between a mobile station and a femto base station to measure a location of the mobile station, they have the following problem. In the positioning techniques, wireless quality information (e.g., Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ)) acquired from a mobile station, which is a positioning target, is mainly used. Therefore, when measuring a location of the mobile station, an installation situation of the mobile station (e.g., a direction of the mobile station or whether the mobile station is in contact with other object) or a surrounding environment of the mobile station (e.g. a degree of loss in wireless propagation) is not considered, whereby implementation of accurate positioning of the mobile station being impeded. This problem is particularly significant when the mobile station is in contact with another object (e.g., when the user brings the mobile station into contact with their ear for a voice call) or when there is a shielding object in the vicinity of the mobile station (e.g., when the user carries the mobile station in a bag).